1. Field of the Invention
The present invention relates to a lens barrel that houses a zoom lens or any other lens, and particularly to a lens barrel with a small-sized mount that connects the lens barrel to a camera body.
2. Description of the Related Art
A lens barrel used in a single lens reflex camera or other imaging apparatus is equipped with a diaphragm mechanism that is provided in a barrel body and adjusts the amount of light and the depth of field. The diaphragm mechanism of this type is broadly classified into two types: an in-lens driven diaphragm mechanism in which an actuator provided in the barrel body opens/closes a diaphragm, and an externally driven diaphragm mechanism in which a driving force produced by an actuator provided in an imaging apparatus body is transferred to the barrel body via a transfer mechanism formed in a mount to open/close a diaphragm.
Examples of the externally driven diaphragm mechanism include those described in JP-A-60-53912 and JP-A-60-258524. In the lens barrel described in JP-A-60-53912, a driving force produced in a camera body acts on a lens-side transfer mechanism disposed in a mount unit, and the driving force in turn rotates a diaphragm drive member provided integrally with the lens-side transfer mechanism to open/close a diaphragm (FIG. 10 in JP-A-60-53912). The diaphragm drive member fits in the inner opening of a male mount, is positioned in the optical axis direction by a barrel body and held there. In the lens barrel described in JP-A-60-258524, a ring-shaped diaphragm transfer member that operates a diaphragm fits in the inner opening of a lens mount and is restricted in the optical axis direction by a ring-shaped stopper plate fixed between the lens mount and a fixed frame (FIG. 1 in JP-A-60-258524). Each of the diaphragm drive members of the related art, however, restricts its position in the optical axis direction by using a separate member, resulting in increase in the number of parts and increase in size of the barrel body in the optical axis direction.
On the other hand, it is difficult to change the design of a lens barrel in order to reduce the size and weight thereof because of a need for higher magnification, specifically, because the lens diameter, the lens thickness, and the range over which a zoom lens group can move directly affect the function of the lens barrel. Only part of the mechanisms in a barrel body allows design change in terms of reduction in size and weight.
Further, there is a need, in association with a need for multifunctional lens barrels and imaging apparatus bodies, to enlarge a circuit substrate provided in the barrel body in order to provide areas where electronic parts are mounted and circuit patterns are formed. Moreover, it is necessary to provide a space in which motors and other drive systems for moving a zoom lens group and other movable blocks at high speed and positioning them in a precise manner are disposed.